Image-guided surgical procedures typically require placing surgical instruments, for example, catheters, scopes, probes, needles, ultrasound, ablators, drills, therapy delivery, therapy measure, physiological measure, etc., at a particular place, often at a particular orientation as well. Guiding these instruments in real-time is typically with respect to pre-acquired images from an imaging device, such as a computed tomography (CT) device, magnetic resonance imaging (MRI) device, etc., that are aligned with the guidance device. Images can also be acquired during the surgical procedure to update and correct pre-planned procedures, thus ensuring the best results practicable.
One of the best ways of guiding surgical instruments, both internal and external to a body being operated upon, is to use magnetic tracking technology. Numerous U.S. patents disclose magnetic tracking technology. These technologies all rely on a means of generating magnetic fields, sensing magnetic fields, and computing the position and orientation (P&O) of a device using the sensed fields. A drawback of magnetic tracking technology is when a live imaging device, such as an X-ray image intensifier (a/k/a a “C-arm”), is used during the surgical procedure: the device causes significant inaccuracies in the determination of the P&O. This inaccuracy is caused by the distortion of the magnetic field due to the metallic components of the imaging device, which are not accounted for (adequately, or at all) by the magnetic tracking algorithm being used. Many attempts have been made to account for these inaccuracies and are disclosed in numerous U.S. patents.